Present television receivers, such as NTSC (National Television Standards Committee) television receivers, include video processing circuitry that typically must process a video signal conforming to only a single, predetermined video format. Future digital television (DTV) receivers are expected to be implemented substantially in accordance with the transmission standards established by the Advanced Television Standards Committee (ATSC). A similar standard is the European Digital Video Broadcasting (DVB) standard. A compressed digital video system is described in the ATSC digital television standard document A/53, incorporated herein by reference. Moreover, the Moving Pictures Experts Group (MPEG) has promulgated several standards relating to digital data delivery systems. The first, known as MPEG-1, refers to ISO/IEC standards 11172 and is incorporated herein by reference. The second, known as MPEG-2, refers to ISO/IEC standards 13818 and is incorporated herein by reference. The new DTV standards allow broadcasters to deliver virtually any format up to 1920.times.1080 pixels. Specifically, DTV receivers must be capable of receiving source video comprising image sequences that vary in spatial resolution (480 lines, 720 lines, or 1080 lines), in temporal resolution (60 fps, 30 fps, or 24 fps), and in scanning format (2:1 interlaced or progressive scan).
It is known in the computer industry to display multiple graphics formats on a so-called "multisync" display device. Specifically, a multisync display changes horizontal and/or vertical scanning frequencies in response to a change in graphics format. Such a multisync approach may be implemented in a video or television environment by using, e.g., studio equipment raster formats standardized by the Society of Motion Picture and Television Engineers (SMPTE). Unfortunately, the multisync approach leads to an increase in cost due to the more complicated deflection circuitry, an increase in power consumption, and a high inter-format switching latency (i.e., greater than one video frame) due to long time constants associated with deflection coil inductance.
A better approach was disclosed by Lee in U.S. Pat. No. 5,485,216, issued Jan. 16, 1996 for Video Conversion Apparatus for High Definition Television, incorporated herein by reference in its entirety. In the Lee patent, a high definition television signal is decoded, then converted to a 30 Hz frame rate, then vertically decimated, then horizontally decimated and then interleaved to produce a 30 Hz, 1050 vertical scanning line video signal. Thus, the Lee arrangement provides a brute force technique for converting a high definition television signal into a 30 Hz, 1050 vertical scanning line video signal. The format-converted television signal is then processed in a conventional manner to produce a picture.
Unfortunately, the Lee arrangement disadvantageously requires complex timing, switching and video processing circuitry. Moreover, the Lee arrangement merely provides a front-end format converter to a standard display device.
Therefore, a need exists in the art for a cost-effective video processing system suitable for use in, e.g., a multiple format television receiver. It is also seen to be desirable to provide a video system that advantageously utilizes display timing processing that, unlike prior art front-end video processing systems, comprehensively reduces total system cost and complexity.